This invention relates to the field of melting aluminum. Current melting technology for aluminum is based largely on the reverberatory furnace which uses natural gas or other energy forms to heat aluminum. The generated heat is transferred to the aluminum by means of radiation and convection between gas and solid materials. However, this process is inefficient because it results in high gas consumption, large volume of combustion products or "off gases," and long processing times.
A bath of molten salt has been used to heat metals such as steel and its alloys. The use of a bath of molten salt as a medium for transferring heat from a heat source to the aluminum to be melted has an advantage over the reverbatory furnace in that the heat convection from the molten salt to the solid aluminum is more thermally efficient than the use of gas to transfer heat to the solid aluminum. Molten salts or fluxes have been proposed as mediums for refining or heating aluminum and alloys thereof in U.S. Pat. Nos. 4,038,068, 4,511,398, 4,568,430, 4,576,690, and 4,761,207. The processes described in these patents are generally associated with disadvantages, such as adjustments which are required of the salt bath composition, complexity of procedures used for separating aluminum from the molten salt, complexity of procedures for removing contaminants from molten salt, and the number of steps in which affirmative action or electrochemical intervention is required to maintain overall continuity of the process. Moreover, none of these processes particularly address the need for an inexpensive and efficient means for heating the salt bath by natural gas in connection with transferring the generated heat through an efficient and practical means to solid aluminum. A need therefore exists for a melter which combines thermal efficiency and compactness of design.